This invention relates to an ink jet printhead. More particularly, the invention relates to a nozzle guard for an ink jet printhead.
Our co-pending patent application, U.S. patent application Ser. No. 09/575,141, incorporated herein by reference, discloses a nozzle guard for an ink jet printhead. The array of nozzles is formed using micro-electromechanical systems (MEMS) technology, and has mechanical structures with sub-micron thicknesses. Such structures are very fragile, and can be damaged by contact with paper, fingers, and other objects. The present invention discloses a nozzle guard to protect the fragile nozzles and keep them clear of paper dust.
According to the invention, there is provided a printhead for an ink jet printer, the printhead comprising
at least one printhead chip, said at least one printhead chip comprising
a substrate; and
a plurality of nozzle arrangements positioned on the substrate, each nozzle arrangement comprising
nozzle chamber walls and a roof wall that define a nozzle chamber, the roof wall defining at least one ink ejection port; and
an ink ejection mechanism that is operatively positioned with respect to the nozzle chamber to eject ink from the at least one ink ejection port on displacement of the ink ejection mechanism; and
a nozzle guard that is positioned on the, or each respective, printhead chip, the nozzle guard comprising
a body member that is spaced from and spans the printhead chip, the body member defining a plurality of passages that extend through the body member, the body member being positioned so that each passage is aligned with one of the ink ejection ports, a thickness of the body member and a cross sectional area of each passage being such that ink ejected from the ink ejection ports can pass through the passages; and
a support structure that is interposed between the body member and the printhead chip, the support structure being configured to permit the flow of air into a space defined between the body member and the printhead chip and through each passage to keep the passages clear of particles.
The substrate may be in the form of a silicon wafer substrate. Each nozzle arrangement may be the product of an integrated circuit fabrication process carried out on the silicon wafer substrate so that the nozzle arrangement defines a micro-electromechanical system.
The support structure may be defined by a plurality of struts that are interposed between the body member and the printhead chip.